1. Field of the Invention
The present invention relates to a catalyst component for ethylene polymerization and copolymerization with other olefins.
2. Description of the Prior Art
The scientific literature (publication and patent literature) contains numerous examples of catalyst components for the homo- and copolymerization of ethylene. The following are exemplary as describing unsupported catalyst components:
1. European Patent Publication No. 140,536 describes a titanium halide-containing catalyst prepared by (1) reacting a magnesium hydrocarboyloxide with a silicon compound having at least one hydrogen-silicon bond; (2) contacting the resulting product with an electron donor; and (3) contacting the resulting product with a titanium halide;
2. PCT International Publication No. WO 88/05056 describes a catalyst component obtained by (1) treating an organomagnesium compound without chlorine with a solid silane compound containing one or two hydroxyl groups and (2) then with a titanium halide compound; and
3. European Patent Publication No. 261,808 describes formation of a catalyst component, useful in the polymerization of ethylene-propylene copolymer rubber, which is formed by contacting a metal oxide with a magnesium compound, such as a dialkylmagnesium, and subsequently contacting the resulting product with a titanium compound, such as titanium tetrachloride, or, optionally, first with an alcohol or a silicon compound. 4. U.S. Pat. No. 5,063,188 to D. B. Malpass describes a catalyst component formed by reaction of an organomagnesium compound and a tetraalkyl silicate, contact of the resulting product with a chlorinating reagent, and treatment of the product from that previous step with liquid titanium halide.
Examples of the synthesis of supported catalyst components are provided in the following:
1. U.S. Pat. Nos. 4,378,304 and 4,458,058 to R. A. Dombro describe reaction of a support with a Group IIA organometallic compound free of aluminum alkyls, reaction of the resulting product with water or a hydrocarbyl alcohol, then reaction of that product with, for example, titanium tetrachloride.
2. U.S. Pat. No. 4,396,533 to A. Johnstone heats a refractory oxide support having surface hydroxyl with, for example, an organic derivative of a metal, such as tetraethyl silicate, followed by reaction of the resulting product with one or more organometallic compounds, followed by impregnation of the resulting solid product with a halogen-containing transition metal compound, such as titanium tetrachloride.
3. U.S. Pat. No. 4,481,301 to T. E. Nowlin et al. treats a support with an organomagnesium composition and then suspends the supported magnesium composition thus formed in a liquid medium with a tetravalent titanium compound.
4. European Patent Publication No. 261,808 contacts a metal oxide with an organomagnesium compound, then contacts the resulting composition, optionally, first with an alcohol or silicon compound (which can either contain hydrocarbyloxy groups or halogen atoms) and then with a titanium compound and an organoaluminum compound.
High density ethylene homopolymers are widely used in injection molding operations. Advantageously such resins, when used in injection molding operations, should have a narrow molecular weight distribution (MWD) which is largely determined by the nature of the catalyst. The catalyst should also exhibit other desirable characteristics for commercial use. The catalyst productivity should be as high as possible so that the resin will have low catalyst residue. It is also very desirable that the catalyst result in a polymer having a large particle size and high bulk density. Another desirable characteristic of the catalyst is that it have a high hydrogen response. A high hydrogen response means that small increases in the amount of hydrogen used in the reactor will result in substantial decrease in molecular weight and a higher melt index polymer.